Blizzard has announced the first Diablo IV expansion. Vessel of Hatred will arrive in late 2024 and introduce a new class while revealing the fate of the villain Mephisto.
Disagree with the "anyway" thing. Traditionally, Diablo games haven't grown their legs until the expansion/revision; where they became completely different (and better) games. This was true with D2/LoD, and certainly true with D3/RoS.